We reanalyze previous experimental measurements of solid volume fraction, mean velocity, and velocity fluctuations in collisional suspensions of plastic cylinders and water flowing over inclined, erodible beds. We show that the particle pressure scales with the granular temperature, as predicted by kinetic theory of granular gases. The assumption that the particle shear stress is also well predicted by kinetic theory permits us to determine the fluid shear stress and the effective fluid viscosity from the experiments. The fluid viscosity can be decomposed into turbulent and granularlike components: the turbulent viscosity can be modeled using a mixing length, which is a decreasing function of the local volume fraction and does not depend upon the distance from the bed; the granularlike viscosity, associated with the transfer of momentum due to the conjugate motion of the fluid mass added to the particles, can be modeled by replacing the particle density with the density of the added fluid mass in the viscosity of kinetic theory.

By performing large-scale density-matrix renormalization group simulations, we investigate a one-dimensional correlated bosonic lattice model with a synthetic spin-orbit coupling realized in recent experiments. In the insulating regime, this model exhibits a symmetry-protected topological phase. This symmetry-protected topological phase is stabilized by time-reversal symmetry and it is identified as a Haldane phase. We confirm our conclusions further by analyzing the entanglement spectrum. In addition, we find four conventional phases: a Mott insulating phase with no long range order, a ferromagnetic superfluid phase, a ferromagnetic insulating phase, and a density-wave phase.

The dynamics of water in polyethylene oxide (PEO)/LiCl solution has been studied with quasielastic neutron scattering experiments and molecular dynamics (MD) simulations. Two different time scales of water diffusion representing interfacial water and bulk water dynamics have been identified. The measured diffusion coefficient of interfacial water remained 5–10 times smaller than that of bulk water, but both were slowed by approximately 50% in the presence of ${\mathrm{Li}}^{+}$. Detailed analysis of MD trajectories suggests that ${\mathrm{Li}}^{+}$ is favorably found at the surface of the hydration layer, and the probability to find the caged ${\mathrm{Li}}^{+}$ configuration formed by the PEO is lower than for the noncaged ${\mathrm{Li}}^{+}-\mathrm{PEO}$ configuration. In both configurations, however, the slowing down of water molecules is driven by reorienting water molecules and creating water-${\mathrm{Li}}^{+}$ hydration complexes. Performing the MD simulation with different ions (${\mathrm{Na}}^{+}$ and ${\mathrm{K}}^{+}$) revealed that smaller ionic radius of the ions is a key factor in disrupting the formation of PEO cages by allowing spaces for water molecules to come in between the ion and PEO.

We present the third-order QCD prediction for the production of top antitop quark pairs in electron-positron collisions close to the threshold in the dominant $S$-wave state. We observe a significant reduction of the theoretical uncertainty and discuss the sensitivity to the top quark mass and width.

Smoothing is an estimation method whereby a classical state (probability distribution for classical variables) at a given time is conditioned on all-time (both earlier and later) observations. Here we define a smoothed quantum state for a partially monitored open quantum system, conditioned on an all-time monitoring-derived record. We calculate the smoothed distribution for a hypothetical unobserved record which, when added to the real record, would complete the monitoring, yielding a pure-state “quantum trajectory.” Averaging the pure state over this smoothed distribution yields the (mixed) smoothed quantum state. We study how the choice of actual unraveling affects the purity increase over that of the conventional (filtered) state conditioned only on the past record.

We show that the excess events observed in a number of recent LHC resonance searches can be simultaneously explained within a nonsupersymmetric left-right inverse seesaw model for neutrino masses with $W_R$ mass around 1.9 TeV. The minimal particle content that leads to gauge coupling unification in this model predicts $g_R\simeq 0.51$ at the TeV scale, which is consistent with data. The extra color singlet, $SU(2)$-triplet fermions required for unification can be interpreted as the dark matter of the Universe. Future measurements of the ratio of same-sign to opposite-sign dilepton events can provide a way to distinguish this scenario from the canonical cases of type-I and inverse seesaw, i.e., provide a measure of the relative magnitudes of the Dirac and Majorana masses of the right-handed neutrinos in the $SU(2{)}_R$ doublet of the left-right symmetric model.

Quasi-two-dimensional itinerant fermions in the antiferromagnetic (AFM) quantum-critical region of their phase diagram, such as in the Fe-based superconductors or in some of the heavy-fermion compounds, exhibit a resistivity varying linearly with temperature and a contribution to specific heat or thermopower proportional to $T\ln T$. It is shown, here, that a generic model of itinerant anti-ferromagnet can be canonically transformed so that its critical fluctuations around the AFM-vector $Q$ can be obtained from the fluctuations in the long wavelength limit of a dissipative quantum $XY$ model. The fluctuations of the dissipative quantum $XY$ model in 2D have been evaluated recently, and in a large regime of parameters, they are determined, not by renormalized spin fluctuations, but by topological excitations. In this regime, the fluctuations are separable in their spatial and temporal dependence and have a spatial correlation length which is proportional to the logarithm of the temporal correlation length, i.e., for some purposes, the effective dynamic exponent $z=\infty$. The time dependence gives $\omega /T$ scaling at criticality. The observed resistivity and entropy then follow. Several predictions to test the theory are also given.

The question of whether electron-electron interactions can drive a metal to insulator transition in graphene under realistic experimental conditions is addressed. Using three representative methods to calculate the effective long-range Coulomb interaction between $\pi$ electrons in graphene and solving for the ground state using quantum Monte Carlo methods, we argue that, without strain, graphene remains metallic and changing the substrate from ${\mathrm{SiO}}_2$ to suspended samples hardly makes any difference. In contrast, applying a rather large—but experimentally realistic—uniform and isotropic strain of about 15% seems to be a promising route to making graphene an antiferromagnetic Mott insulator.

We show that, because of the inevitable twist and lattice mismatch in heterobilayers of transition metal dichalcogenides, interlayer excitons have sixfold degenerate light cones anomalously located at finite velocities on the parabolic energy dispersion. The photon emissions at each light cone are elliptically polarized, with the major axis locked to the direction of exciton velocity, and helicity specified by the valley indices of the electron and the hole. These finite-velocity light cones allow unprecedented possibilities for optically injecting valley polarization and valley current, and the observation of both direct and inverse valley Hall effects, by exciting interlayer excitons. Our findings suggest potential excitonic circuits with valley functionalities, and unique opportunities to study exciton dynamics and condensation phenomena in semiconducting 2D heterostructures.

The statistics of Poincaré recurrences is studied for the base-pair breathing dynamics of an all-atom DNA molecule in a realistic aqueous environment with thousands of degrees of freedom. It is found that at least over five decades in time the decay of recurrences is described by an algebraic law with the Poincaré exponent close to $\beta =1.2$. This value is directly related to the correlation decay exponent $\nu =\beta -1$, which is close to $\nu \approx 0.15$ observed in the time resolved Stokes shift experiments. By applying the virial theorem we analyze the chaotic dynamics in polynomial potentials and demonstrate analytically that an exponent $\beta =1.2$ is obtained assuming the dominance of dipole-dipole interactions in the relevant DNA dynamics. Molecular dynamics simulations also reveal the presence of strong low frequency noise with the exponent $\eta =1.6$. We trace parallels with the chaotic dynamics of symplectic maps with a few degrees of freedom characterized by the Poincaré exponent $\beta \sim 1.5$.

We introduce a coarse-graining transformation for tensor networks that can be applied to study both the partition function of a classical statistical system and the Euclidean path integral of a quantum many-body system. The scheme is based upon the insertion of optimized unitary and isometric tensors (disentanglers and isometries) into the tensor network and has, as its key feature, the ability to remove short-range entanglement or correlations at each coarse-graining step. Removal of short-range entanglement results in scale invariance being explicitly recovered at criticality. In this way we obtain a proper renormalization group flow (in the space of tensors), one that in particular (i) is computationally sustainable, even for critical systems, and (ii) has the correct structure of fixed points, both at criticality and away from it. We demonstrate the proposed approach in the context of the 2D classical Ising model.

We study a one-dimensional quantum problem of two particles interacting with a third one via a scale-invariant subcritically attractive inverse square potential, which can be realized, for example, in a mixture of dipoles and charges confined to one dimension. We find that above a critical mass ratio, this version of the Calogero problem exhibits the generalized Efimov effect, the emergence of discrete scale invariance manifested by a geometric series of three-body bound states with an accumulation point at zero energy.

We study the effects of integrability-breaking perturbations on the nonequilibrium evolution of many-particle quantum systems. We focus on a class of spinless fermion models with weak interactions. We employ equation of motion techniques that can be viewed as generalizations of quantum Boltzmann equations. We benchmark our method against time-dependent density matrix renormalization group computations and find it to be very accurate as long as interactions are weak. For small integrability breaking, we observe robust prethermalization plateaux for local observables on all accessible time scales. Increasing the strength of the integrability-breaking term induces a “drift” away from the prethermalization plateaux towards thermal behavior. We identify a time scale characterizing this crossover.